Heat the oven: Preheat to 400°F (200°C).
Line a sheet pan with parchment for easy cleanup.
Season the salmon: Pat fillets dry. Brush with olive oil, then season with salt, pepper, and a pinch of red pepper flakes if you like heat.
Roast: Bake for 10–12 minutes, depending on thickness. You want the salmon just opaque and flaky with a slight gloss in the center.
Make the lemon butter: In a small pan over low heat, melt 3–4 tablespoons butter.
Add minced garlic and cook 30–60 seconds until fragrant, not browned. Stir in lemon zest and 1–2 tablespoons lemon juice. Season with salt and pepper.
Add chopped dill or parsley.
Prep the bowl base: Toss mixed greens with a drizzle of olive oil, a squeeze of lemon, and a pinch of salt. Slice cucumber and avocado. Halve cherry tomatoes if using.
Assemble: Add greens to bowls.
Top with salmon (flake it or leave it whole), cucumber, avocado, and a few capers. Spoon warm lemon butter over the salmon and greens.
Finish and serve: Add extra herbs and fresh pepper. Taste and adjust with more lemon if needed.